The present invention relates to an electric motor, in particular a wiper motor for operating a device for wiping of a window of a motor vehicle, a series of electric motors, in particular wiper motors, as well as to a method of producing an electric motor.
Numerous electric motors for operation of a wiper device are known and produced in great numbers. In connectionally produced series of electric motors manufacturing and material tolerances result in dissipation of given-out power of the individual electric motors. In order to reliably operate a wiping device, the electric motor is designed so that the weakest electric motor of the series must be suitable for operation of the wiping device. It is however problematic to design the wiping device so that, in particular in the case of blockage, it can not be damaged by the strongest electric motor of the series. The movable parts of the wiping device must be much stabler than required for normal operation of the wiper device.
This forced overdimensioning increases the material for manufacturing cost and increases the dimensions and therefore the space required for the wiper device in the motor vehicle.
Accordingly, it is an object of the present invention to provide an electric motor of the above mentioned general type which has the advantage of a power limitation by a parameter is realized in a very simple and fast way at the end of a series manufacture. Conventional electric motors for operation of a wiping device are designed with an electronic system for control/regulation in which such a power limitation is not easily implemented.
When the electric motor is designed in accordance with the present invention, it eliminates the disadvantages of the prior art and provides for the highly advantageous results.
It is especially advantageous when the control device has a signal input for supplying the parameter, the nominal torque or an axial torque for supplying the parameter itself, or one or several variables for determination of the parameter into the control device.
It is further advantageous when the control device has a memory device for storing the parameter. In this manner the parameter must be supplied in a short time, for example during a monitoring at the end of a manufacturing line. It remains there until a change or until the end of the service life of the electric motor.
In accordance with another advantageous feature of the invention, when the control device is formed as an electronic control device, there are all possibilities to make available a modern control or regulation. In this matter, also complex algorithms can be utilized for control/regulation.
In accordance with another advantageous feature of the invention, when the electronic control device has a microcontroller for computation and/or storage of the parameter, then the storage and control complexity is further increased.
In accordance with another advantageous feature of the invention, when the microcontroller is formed so that from the supplied nominal and/or actual torque the parameter can be determined, then the time and labor expenses during a band end testing are reduced to a minimum and thereby the costs are further reduced.
Furthermore, it is advantageous when the parameter is formed from the quotients of nominal torque and actual torque, since this linear statement is easy to handle and is sufficiently accurate for many cases.
A series of electric motors, which are provided with a parameter for power limitation, wherein all electric motors from the series layer produce the same nominal torque, has the advantage that an accurately adjusted design of the linkage of the wiping device is possible, since the linkage of the wiping device must not receive any power overcapacity of the electric motor.
The method of producing an electric motor of the present invention has the advantage that all electric motors which are produced with this method are exactly limited as to their output power or their torque.
When the power variables are determined by mechanical braking of the driven electric motor with simultaneous measurement of a further characteristic value, that it is especially advantageous since as a rule during a band end control at the end of a manufacturing band a testing run is performed, and therefore for programming of the control device can occur directly after the end of the testing run. The braking process at the end of the testing run can be used for determination of the power variable.